Weird Bang/Cold Start Noise (2015 LX570)

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Frosties

Joined
Jul 23, 2021
Threads
7
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36
Location
Dubai, UAE
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This morning, 30 seconds after I started the engine, I heard this weird loud idling noise. I've never heard it before. It stopped right as the video ends. Lasted for all of 30 seconds. It sounded quite worrying in person. The video was taken inside the cabin with all the doors closed.

For context, I had the PCV valve changed a few days ago. A few weeks prior, I heard this loud bang from underneath the car towards the passenger side while on the highway. It sounded a gunshot. That bang happened twice again a few hours later. I wasn't able to get it on video because it lasts half a second. I'm not sure if the two noises are even related. No engine warning light or anything.

What is going on with my LX570? I've serviced it regularly and done all the preventative maintenance possible.
 
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I can hear something but I can't really discern what it is. I do find cell phones often don't capture the sounds anywhere near the same as in person. Or maybe it's my ears after years of standing in front of guitar amps. Does this just happen at cold startup? Is the oil level is good?

Maybe 2 years ago my wife told me she accelerated a bit fast from a stop sign in our neighborhood and hear a big pop or bang. I couldn't find anything wrong when I looked, but I did notice the engine cover was not aligned and had popped off. I snapped it back and it's been quiet since. I think in my case the cover came loose and smacked into the underside of the hood. Might be a long shot for the bang you described but worth checking as they're just pressure-clips holding the cover in place I think.
 
cant hear anything. As linuxgod mentioned, cellphone have good noise cancellation tech and if we are trying to capture the noise, it doesn't help :)
 
The gun shot sounds you described would have me looking for a loose nut/bolt somewhere that is popping under stress. Engine sounds like a normal toyota to me in the video.
 
linuxgod said:
I can hear something but I can't really discern what it is. I do find cell phones often don't capture the sounds anywhere near the same as in person. Or maybe it's my ears after years of standing in front of guitar amps. Does this just happen at cold startup? Is the oil level is good?

Maybe 2 years ago my wife told me she accelerated a bit fast from a stop sign in our neighborhood and hear a big pop or bang. I couldn't find anything wrong when I looked, but I did notice the engine cover was not aligned and had popped off. I snapped it back and it's been quiet since. I think in my case the cover came loose and smacked into the underside of the hood. Might be a long shot for the bang you described but worth checking as they're just pressure-clips holding the cover in place I think.
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Thank you for your insight. Indeed it does sound a bit muted on camera, but the noise was so distinctive and unusual that my passenger and I stopped what we were doing for 30 seconds to listen to where it could be coming from. It sounded like it was coming from the AC vents but the AC was off. It never happened before, but I am concerned something broke.

Edit: If you compare the last second with the rest of the video, you can hear the difference.
 
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jivewalker said:
The gun shot sounds you described would have me looking for a loose nut/bolt somewhere that is popping under stress. Engine sounds like a normal toyota to me in the video.
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Hopefully it’s just that. I think I’ll just ask the mechanic to hook up a scan tool on my next service. Thank you.
 
pvchaitanya said:
cant hear anything. As linuxgod mentioned, cellphone have good noise cancellation tech and if we are trying to capture the noise, it doesn't help :)
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You’re right, it does sound normal on video. If I had kept recording, it would probably be more obvious. Might just ignore that noise.

Edit: If you compare the last second with the rest of the video, you can hear the difference.
 
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A common noise for the 5.7L in higher miles is the chain tensioner. If the car was sitting for some days, that would be a reason for the chain tensioner noise too as it relies on oil pressure.

Not sure how this would be related to a gunshot noise however.
 
TeCKis300 said:
A common noise for the 5.7L in higher miles is the chain tensioner. If the car was sitting for some days, that would be a reason for the chain tensioner noise too as it relies on oil pressure.

Not sure how this would be related to a gunshot noise however.
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Would that problem fix itself? I daily drive this car and frequent highways with it. Drove it the night before this video was recorded and even checked the oil level (as I was trying to see if the PCV valve change improved the oil consumption issue) and it was right on the top dot.

I did switch to 5w-40 oil for the last two services. Before that, I believe the dealer was using 5w-30.
 
I can't tell from your video, but is this the cold start noise? That would be the chain tensioner.

My car does it occasionally after a longer maybe one week sit and oil pressure bleeds down. Others have reported similar. It's a very common thing in the Tundra/Sequoia world. It seems to lessen with a slight increase of oil viscosity, maybe 0W-30 or 5W-30. Not sure I would recommend 5w-40.

The cold start may stay like this for a long time and get no worse for wear. Or if it gets worse, than a replacement tensioner is the fix. Lots of youtube vids.

 
TeCKis300 said:
I can't tell from your video, but is this the cold start noise? That would be the chain tensioner.

My car does it occasionally after a longer maybe one week sit and oil pressure bleeds down. Others have reported similar. It's a very common thing in the Tundra/Sequoia world. It seems to lessen with a slight increase of oil viscosity, maybe 0W-30 or 5W-30. Not sure I would recommend 5w-40.

The cold start may stay like this for a long time and get no worse for wear. Or if it gets worse, than a replacement tensioner is the fix. Lots of youtube vids.

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That actually could be it. I hope it doesn’t happen again because I’ve already spent a ton on repairs on this truck beyond normal maintenance items and can’t be bothered to keep going into the garage every other week to repair the next thing. I mean it hasn’t even done 100,000 miles yet, and I’ve already had so many things go wrong with it despite doing every preventative maintenance item I can.

Regarding the oil, I have asked around garages, spare parts shops, and even on here (You can see the post on my profile) because I was wary of using it, but the consensus was that 5w-40 is recommended for where I live (Dubai). The ‘Lexus Genuine Motor Oil’ sold here only comes in 5w-40 fully synthetic, and it’s by far the most widely used oil for these trucks. I don’t mind switching to 5w-30, but during summer months it frequently gets up to 45°C (113°F) here but only as low as 5°C (41°F) in the winter if that.
 
Frosties said:
That actually could be it. I hope it doesn’t happen again because I’ve already spent a ton on repairs on this truck beyond normal maintenance items and can’t be bothered to keep going into the garage every other week to repair the next thing. I mean it hasn’t even done 100,000 miles yet, and I’ve already had so many things go wrong with it despite doing every preventative maintenance item I can.

Regarding the oil, I have asked around garages, spare parts shops, and even on here (You can see the post on my profile) because I was wary of using it, but the consensus was that 5w-40 is recommended for where I live (Dubai). The ‘Lexus Genuine Motor Oil’ sold here only comes in 5w-40 fully synthetic, and it’s by far the most widely used oil for these trucks. I don’t mind switching to 5w-30, but during summer months it frequently gets up to 45°C (113°F) here but only as low as 5°C (41°F) in the winter if that.
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Ah, thanks for clarifying. Dubai is a whole other world I'm not familiar with and I would go with the local recommendations.
 
I have had this same issue on a 2013 LX for about 6 months or so. After the truck is warm, the noise doesn't come on at all. At some point I thought it was a pulley but good to know it is a tension er.
 
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